1. Field of the Invention
Embodiments of the present invention generally relate to an apparatus and method for plasma assisted deposition. More particularly, embodiments of the present invention relate to an apparatus and method of plasma assisted deposition by generation of a plasma adjacent a processing region.
2. Description of the Related Art
Reliably producing sub-micron and smaller features is one of the key technologies for the next generation of very large scale integration (VLSI) and ultra large scale integration (ULSI) of semiconductor devices. However, as the fringes of circuit technology are pressed, the shrinking dimensions of interconnects in VLSI and ULSI technology have placed additional demands on the processing capabilities. The multilevel interconnects that lie at the heart of this technology require precise processing of high aspect ratio features, such as vias and other interconnects. Reliable formation of these interconnects is very important to VLSI and ULSI success and to the continued effort to increase circuit density and quality of individual substrates.
As circuit densities increase, the widths of vias, contacts and other features, as well as the dielectric materials between them, decrease to sub-micron dimensions (e.g., less than 0.20 micrometers or less), whereas the thickness of the dielectric layers remains substantially constant, with the result that the aspect ratios for the features, i.e., their height divided by width, increases. Many traditional deposition processes have difficulty filling sub-micron structures. Therefore, there is a great amount of ongoing effort being directed at the formation of substantially void-free and seam-free sub-micron features having high aspect ratios.
Atomic layer deposition is one deposition technique being explored for the deposition of material layers over features having high aspect ratios. One example of atomic layer deposition comprises the sequential introduction of pulses of gases. For instance, one cycle for the sequential introduction of pulses of gases may comprise a pulse of a first reactant gas, followed by a pulse of a purge gas and/or a pump evacuation, followed by a pulse of a second reactant gas, and followed by a pulse of a purge gas and/or a pump evacuation. Sequential introduction of separate pulses of the first reactant and the second reactant is intended to result in the alternating self-limiting adsorption of monolayers of the reactants on the surface of the substrate and, thus, forms a monolayer of material for each cycle. The cycle is repeated to a desired thickness of the deposited material. A pulse of a purge gas and/or a pump evacuation between the pulses of the first reactant gas and the pulses of the second reactant gas is intended to promote reaction of the first reactant gas and the second reactant gas at the surface of a substrate by limiting gas phase reactions.
FIG. 1 is a schematic cross-sectional view of a prior art chamber 10 adapted for chemical vapor deposition. The chamber 10 includes a showerhead 40 and a substrate support 32 for supporting a substrate 36. The showerhead 40 has a central gas inlet 44 for the injection of gases and has a plurality of holes 42 to accommodate the flow of gases therethrough. A power source 70, such as an RF power source, is coupled to the showerhead 40 to create an electric field between the shower head 40 and the substrate support 32 generating a plasma 80 therebetween. One problem with the use of prior chambers, such as chamber 10, for atomic layer deposition requiring a plasma 80 is that the plasma 80 may etch or remove deposited materials on the surface of the substrate 36 due to the ion bombardment or sputtering by the plasma 80 of the deposited material on the substrate 36 which is particularly detrimental in atomic layer deposition in which a monolayer of material is desired to be deposited per cycle of gases.
Prior attempts to perform atomic layer deposition also include generating a plasma through a remote plasma source separate from the processing chamber and directing the atomic species into the processing chamber for reaction. One problem associated with these prior attempts is that the atomic species may easily recombine preventing the reaction of the atomic species on the surface of the substrate.
Thus, there is a need for an improved apparatus and method of generating a plasma in deposition processes.